A vehicle air-conditioning device described in Patent Literature 1 compresses a refrigerant by driving a compressor on an engine drive force. On the contrary, an electric compressor driven by an electric motor is adopted in a vehicle air-conditioning device installed to an electrically-driven vehicle, such as an electric vehicle and a hybrid vehicle, which has been becoming popular in recent years. For example, a hybrid vehicle adopting an electric compressor is capable of operating the air-conditioning device even when an engine is at rest.